Further evaluation of long-chain alkenones as indicators of paleoceanographic conditions

doi:10.1016/0016-7037(88)90132-9

Geochimica et Cosmochimica Acta

Volume 52, Issue 9, September 1988, Pages 2303-2310

https://doi.org/10.1016/0016-7037(88)90132-9 Get rights and content

Abstract

Cultures of the marine coccolithophorid, Emiliania huxleyi, were grown in the laboratory at five temperatures (8°, 10°, 15°, 20°, 25°C) and monitored by capillary gas chromatography for their long-chain, unsaturated lipid compositions. The long-chain lipids of this plant comprise a series of C₃₇, C₃₈ and C₃₉ di-, tri- and, in cells grown below 15°C, tetra-unsaturated methyl and ethyl ketones and a methyl and ethyl ester of a di-unsaturated C₃₆ fatty acid. Systematic changes in the degree of unsaturation and in the overall carbon chain length distribution of the alkenones and in the proportion of fatty acid esters relative to alkenones are noted as a function of growth temperature. We present temperature calibrations for these changes in the lipid composition of laboratory cultures and compare these results with the compositions of this biomarker series measured in a variety of sediments accumulating beneath warm (⩾25°C) and cold (⩽12°C) surface waters in the tropical and temperate North Pacific Ocean, respectively. The comparisons demonstrate 1) this series of biomarkers is deposited in these oceanic sediments with minimal evidence of alteration to its original composition and 2) the strain of E. huxleyi used in this laboratory calibration is representative of the “average” marine phytoplankton supplying this novel series of biomarkers to contemporary sediments in these two environments and a wide variety of other oceanic environments. The long-chain alkenones constitute a major component (8.0 ± 2.9%) of the total organic carbon content of living cells of E. huxleyi. The high cellular abundance of these compounds appears to be relatively constant and independent of the growth temperature of the plant. These biomarkers provide a well-designed and useful geochemical tool for assessing variations not only in surface water temperatures but potentially also in the productivity of an important group of marine phytoplankton in oceans of the recent and distant past.

References (27)

J.W De Leeuw et al.
On the occurrence and structural identification of long chain unsaturated ketones and hydrocarbons in sediments
C.J Lorenzen
A method for the continuous measurements of in vivo chlorophyll concentration
Deep-Sea Res.
(1966)
H Okada et al.
The distribution of oceanic coccolithophorids in the Pacific
Deep-Sea Res.
(1973)
F.G Prahl et al.
Hydrocarbons in Washington coastal sediments
Estuar. Coast. Shelf Sci.
(1984)
F.G Prahl et al.
A geochemical study of longchain n-aldehydes in Washington coastal sediments
Geochim. Cosmochim. Acta
(1987)
J.K Volkman et al.
Novel unsaturated straight chain C₃₇-C₃₉ methyl and ethyl ketones in marine sediments and a coccolithophore Emiliania huxleyi
J.K Volkman et al.
Some analyses of lipid classes in marine organisms, sediments and seawater using thin-layer chromatography-flame ionisation detection
J. Chrom.
(1986)
S.C Brassell et al.
Palaeoclimatic signals recognized by chemometric treatment of molecular stratigraphic data
Org. Geochem.
(1986)
S.C Brassell et al.
Molecular stratigraphy: A new tool for climatic assessment
Nature
(1986)
R.J Conover et al.
Probable loss of chlorophyll-derived pigments during passage through the gut of zooplankton and some of the consequences
Limnol. Oceanogr.
(1986)

E.D.S Corner et al.

Copepod faecal pellets and the vertical flux of biolipids

P.A Cranwell

Long-chain unsaturated ketones in recent lacustrine sediments

Geochim. Cosmochim. Acta

(1985)

S Emerson

Organic carbon preservation in marine sediments

Cited by (668)

Abrupt cooling of cold seasons at the middle-late Holocene transition revealed by alkenone records from North China
2024, Quaternary Science Reviews
In saline lakes, the paleoenvironmental interpretation of long-chain alkenones (LCAs) is difficult due to the inputs of Isochrysidales Group 2i, which are ice-related bloomers. Here, we perform detailed analysis of LCAs and long-chain alkenoates in sediment cores from Lake Daihai in north China. During the late Holocene, alkenone-inferred temperatures and the Group 2i species abundance indicate a long-term warming trend in cold seasons (winter and early spring), possibly driven by regional insolation and by atmospheric CO₂ concentrations. Notably, our records indicate cold climate conditions during the period of 4.3–3.0 cal ka BP, possibly linked to the abrupt expansion of Arctic winter sea ice in a given of low insolation and atmospheric CO₂ concentration conditions. The abrupt cooling may have led to the collapse of the East Aian Summer Monsoon (EASM) and the deterioration of the ecosystems in northern China during the middle to late Holocene transition, and thus likely accounted for the nearly synchronous Chinese Neolithic cultural collapses.
Paleoceanographic importance of tri- and di-unsaturated alkenones through the early phase of Cretaceous Oceanic Anoxic Event 2 from southern high latitudes of the proto-Indian Ocean
2024, Organic Geochemistry
Alkenones are biomarkers derived exclusively from species of haptophyte algae. The relative abundance of di- to tri-unsaturated C₃₇ alkenones expressed as U^K'₃₇ is widely applied as a sea surface paleotemperature proxy for Cenozoic marine sediments. However, the absence of alkatrienones prior to the Eocene has precluded application of the U^K'₃₇ proxy for assessment of Cretaceous paleoclimates. Herein, we report a C₄₀ alkatrienone (tetraconta-9E, 16E, 23E-trien-3-one; C_40:3 Et) in deep-sea sediments from southern high latitudes (International Ocean Discovery Program: IODP site U1516). This discovery extends the geologic record of alkatrienones to the late Cenomanian, ∼70 million years earlier than previous reports. The parallel occurrence of higher abundances of a C₄₀ alkadienone (tetraconta-16E, 23E-dien-3-one; C_40:2 Et) allowed calculation of the U^K’₄₀ unsaturation index, comparable to U^K’₃₇. Stratigraphic variations in the δ¹³C of C_40:2 Et revealed an elevated (∼1.5 ‰) positive carbon isotope excursion (CIE) relative to those observed in carbonate from other OAE2 sequences likely reflecting a decrease in global pCO₂. The U^K’₄₀ profile suggests a concurrent drop in sea surface temperature associated with the decline in pCO₂ during the early phase of OAE2. The timing of these environmental perturbations in the southern high latitude of the proto-Indian Ocean suggests they were triggered by volcanism associated with large igneous province (LIP) formation.
Deciphering the termination of the Messinian salinity crisis: The alkenone record of the Miocene-Pliocene transition in the northern Mediterranean.
2023, Palaeogeography, Palaeoclimatology, Palaeoecology
The late Miocene Messinian salinity crisis (MSC; 5.97–5.33 Ma) transformed the Mediterranean basin into the youngest salt giant in Earth history. The paleoenvironment and the paleodepth of the Mediterranean basin during the terminal phase of the MSC (i.e., the Lago-Mare event), are still uncertain, primarily due to the contradicting presence of in-situ, fully marine vs brackish to freshwater fossils, with different palaeoecological affinity, found in the same rock record. This study uses the distribution of C₃₇, C₃₈ and C₃₉ long-chain unsaturated methyl and ethyl n-ketones (alkenones), produced by haptophyte algae, in combination with micropaleontological and stable oxygen isotope data, to reconstruct the surface water temperatures and paleoenvironmental conditions in the Northern Mediterranean basin across the transition between the latest Miocene Lago-Mare phase to the re-establishment of marine conditions starting in Pliocene, at 5.33 Ma. The results suggest that the Mediterranean basin was already receiving influxes from the Atlantic Ocean before the end of the MSC, resulting in a progressive return to marine conditions proceeding from south to north, i.e., from the more distal to proximal areas. Finally, fully marine conditions were established at the base of the Pliocene (5.33 Ma). The study highlights the reliability of alkenone-based paleo proxies for environmental reconstruction, especially when body fossil records of primary producers are scarce or problematic.
Clumped isotopes in globally distributed Holocene coccoliths reveal their habitat depth
2023, Earth and Planetary Science Letters
Reliable temperature reconstructions are necessary to improve climate reconstructions and comparisons with paleoclimate model simulations. Most existing paleotemperature proxies are based on organic and inorganic remains of marine organisms. Despite the evidence that the habitat depth of coccolithophores and other phytoplankton depend on their ability to balance light, nutrients, and grazing pressure, calibrations of proxies based on photosynthesizers often assume they live in the surface ocean. Here we present the first globally distributed dataset of core top multi-species coccolith clumped isotopes ( $Δ_{47}$ ), which show a clear latitudinal thermal gradient and demonstrate coccolith $Δ_{47}$ sensitivity to temperature. The application of the most recent $Δ_{47}$ -temperature calibration for marine biogenic carbonates yields calcification temperatures implying deep habitats of ∼50 to ∼150 m for tropical coccolithophores, which could photosynthesize with 1-10% of surface photosynthetic active radiation (PAR) levels. Because of the uncertainties of $Δ_{47}$ thermometry and of the low upper ocean temperature gradient, at well-mixed high-latitude locations, coccolith $Δ_{47}$ cannot be used to reliably constrain a specific habitat depth. Nevertheless, $Δ_{47}$ is a good indicator of paleotemperatures of the mixed layer. We also use coccolith $Δ_{47}$ to derive the first regression relating core top coccolith $Δ_{47}$ and sea surface temperatures (SST). Although this formulation cannot be considered a proper coccolith-specific $Δ_{47}$ calibration, since it ignores coccolithophore's potential for calcification at depth, it facilitates comparison with temperature proxies like $U_{37}^{k^{'}}$ , which are regressed to SST, rather than production temperature.
Total synthesis of C<inf>37</inf> alken-2-one temperature geomarkers
2023, Tetrahedron Letters
The total synthesis of the natural (8E,15E,22E)-heptatriaconta-8,15,22-trien-2-one and (15E,22E)-heptatriaconta-15,22-dien-2-one is reported. Our synthesis involved a modular and convergent approach, based on the copper-catalyzed addition of Grignard reagents to allylic olefins. The obtention of these methyl ketones is an important asset for the use of these compounds as analytical patterns with application in Earth sciences.
Exploring the theoretical upper temperature limit of alkenone unsaturation indices: Implications for paleotemperature reconstructions
2023, Organic Geochemistry
The structural specificity, exceptional diagenetic stability, and linear response of unsaturation to temperature have made alkenones an indispensable tool for reconstructing past sea surface temperatures, with the well known $U_{37}^{K'}$ proxy widely applied in the past 40 years. However, $U_{37}^{K'}$ approaches unity at around 28 °C in cultures of Emiliania huxleyi (E. huxleyi), the most widely distributed alkenone producer in global oceans. Recent studies using surface sediments suggest $U_{38 M e}^{K'}$ has ∼1.5 °C higher upper temperature limits than $U_{37}^{K'}$ . However, E. huxleyi generally does not grow above 28 °C. Gephyrocapsa oceanica (G. oceanica), on the other hand, is the dominant alkenone producer when sea surface temperature is above 22 °C and thrives in ocean regions such as the Pacific Warm Pool. So far there have been no culture data for G. oceanica above 29 °C to evaluate the temperature response of alkenone distributions and the (theoretical) upper temperature limit of alkenone unsaturation indices. Here we performed the first culture experiments on two strains of G. oceanica isolated from warm ocean sites at up to 32 °C: RCC6484 from the Pacific Warm Pool and RCC3483 from the South China Sea. We show both strains display higher growth rates at higher temperature, with the highest growth rates at 32 °C (the highest temperature we tested), although alkenone production per cell decreases as temperature increases. Importantly, $U_{37}^{K'}$ and $U_{38 M e}^{K'}$ values of RCC6484 and RCC3483 continue to respond to temperature changes beyond 28 °C, although temperature sensitivity decreases significantly above 28 °C. Above 30 °C, $U_{37}^{K'}$ and $U_{38 M e}^{K'}$ responses to temperature further diminish, limiting their potential for paleo-SST applications using the currently available analytical technology. The ratio of C_38:3 over C_38:2 methyl ketone is on average 11 times higher than the ratio of C_37:3 over C_37:2 from 24 to 32 °C, suggesting a greater potential of using $U_{38 M e}^{K'}$ for paleotemperature reconstruction in high temperature settings.

View all citing articles on Scopus

View full text

Article preview

Geochimica et Cosmochimica Acta

Abstract

References (27)

On the occurrence and structural identification of long chain unsaturated ketones and hydrocarbons in sediments

A method for the continuous measurements of in vivo chlorophyll concentration

Deep-Sea Res.

The distribution of oceanic coccolithophorids in the Pacific

Deep-Sea Res.

Hydrocarbons in Washington coastal sediments

Estuar. Coast. Shelf Sci.

A geochemical study of longchain n-aldehydes in Washington coastal sediments

Geochim. Cosmochim. Acta

Novel unsaturated straight chain C₃₇-C₃₉ methyl and ethyl ketones in marine sediments and a coccolithophore Emiliania huxleyi

Some analyses of lipid classes in marine organisms, sediments and seawater using thin-layer chromatography-flame ionisation detection

J. Chrom.

Palaeoclimatic signals recognized by chemometric treatment of molecular stratigraphic data

Org. Geochem.

Molecular stratigraphy: A new tool for climatic assessment

Nature

Probable loss of chlorophyll-derived pigments during passage through the gut of zooplankton and some of the consequences

Limnol. Oceanogr.

Copepod faecal pellets and the vertical flux of biolipids

Long-chain unsaturated ketones in recent lacustrine sediments

Geochim. Cosmochim. Acta

Organic carbon preservation in marine sediments

Cited by (668)

Abrupt cooling of cold seasons at the middle-late Holocene transition revealed by alkenone records from North China

Paleoceanographic importance of tri- and di-unsaturated alkenones through the early phase of Cretaceous Oceanic Anoxic Event 2 from southern high latitudes of the proto-Indian Ocean

Deciphering the termination of the Messinian salinity crisis: The alkenone record of the Miocene-Pliocene transition in the northern Mediterranean.

Clumped isotopes in globally distributed Holocene coccoliths reveal their habitat depth

Total synthesis of C<inf>37</inf> alken-2-one temperature geomarkers

Exploring the theoretical upper temperature limit of alkenone unsaturation indices: Implications for paleotemperature reconstructions